1. Field of the Present Patent Application
The present patent application is generally directed to a spindle for use with a dose setting mechanism of a drug delivery device. More particularly, the present patent application is generally directed to a spindle for use with drug delivery devices, such as pen type drug delivery devices. Such devices provide for self administration of medicinal product from a multi-dose cartridge and permit a user to set the delivery dose. The present application may find application in both disposable and reusable type drug delivery devices. However, aspects of the invention may be equally applicable in other scenarios as well.
2. Background
Pen type drug delivery devices have application where regular injection by persons without formal medical training occurs. This is increasingly common among patients having diabetes where self-treatment enables such patients to conduct effective management of their disease.
One such prior art pen type drug delivery device is described in
WO 2004/078293 and is illustrated in FIGS. 1 through 12 of the present application. WO 2004/078293 is herein entirely incorporated by reference and to which the reader is directed for any further information.
As illustrated in FIGS. 1 to 5, there is shown a drug delivery device in a plurality of operating positions: for dose setting and for dose administration or injection. The drug delivery device comprises a housing having a first cartridge retaining part 2, and second main (exterior) housing part 4. A cartridge 8 from which a number of doses of a medicinal product may be dispensed is provided in the cartridge retaining part 2. A piston 10 is retained in a first end of the cartridge. A removable cap 12 is releasably retained over a second end of the cartridge retaining part 2.
An insert 16 is provided at a first end of the main housing 4 and is secured against rotational or longitudinal motion. The insert 16 is provided with a threaded circular opening 18. A first helical groove 19 extends from a first end of a spindle 20. The spindle 20 is generally circular in cross section. The first end of the spindle 20 (a distal end) extends through the threaded opening 18 in the insert 16. A second helical groove 24 extends from a second end of the spindle 20 (a proximal end). In the illustrated arrangement, the second helical groove 24 comprises a series of part helical grooves rather than a complete helical groove.
The first helical groove 19 and the second helical groove 24 are oppositely disposed, i.e., the grooves are of opposite hand. The second end of the spindle 20 (i.e., the proximal end) is provided with a receiving recess. A driver 30 extends about the spindle 20 and is provided at a first end with a first radially extending flange 32. A second radially extending flange 34 is provided spaced a distance along the driver 30 from the first flange 32. An intermediate helical groove 36 is provided on an outer part of the driver 30 extending between the first flange 32 and the second flange 34. Further, a part nut 40 is provided engaging the intermediate helical groove 36 and splined to the housing 4 such that part nut 40 does not rotate relative to the housing but is allowed to move axially with respect to the housing 4. A helical groove extends along the entire internal surface of the driver 30. The second helical groove 24 (a male helical groove) of the spindle 20 is adapted to work within said helical groove in the driver.
A shoulder 37 is formed between a second end of the driver 30 (a proximal end of the driver 30) and an extension 38 provided at the second end of the driver 30. The extension 38 has reduced inner and outer diameters in comparison to the remainder of the driver 30. A second end of the extension 38 is provided with a radially outwardly directed flange 39. FIG. 13 illustrates a close up view of the driver 30 and spindle 20 illustrated in FIGS. 1-5.
A clutch 60 is located adjacent the second end of the driver 30. The clutch 60 is generally cylindrical and is provided at a first end (a distal end) with a series of circumferentially directed saw teeth 66 (See, e.g., FIG. 7). Each saw tooth comprises a longitudinally directed surface and an inclined surface. Towards the second end 64 (a proximal end) of the clutch 60 there is located a radially inwardly directed flange 62. The flange 62 of the clutch 60 is disposed between the shoulder 37 of the driver 30 and the radially outwardly directed flange 39 of the extension 38.
The second end of the clutch 60 is provided with a plurality of dog teeth 65 (See, e.g., FIG. 8). The clutch 60 is keyed to the drive sleeve 30 by way of splines (not shown) to prevent relative rotation between the clutch 60 and the drive sleeve 30. In one preferred arrangement, a clicker 50 is provided with said clicker and the clutch 60 each extending approximately half the length of the drive sleeve 30. The clicker 50 and the clutch 60 are engaged as shown in FIGS. 6 and 7, for example.
A dose dial sleeve 70 is provided outside of the clicker 50 and clutch 60 and radially inward of the main housing 4. The dose dial sleeve 70 comprises a distal end and a proximal end. A helical groove 74 is provided about an outer surface of the dose dial sleeve 70. The main housing 4 is provided with a window 44 through which a part of an outer surface of the dose dial sleeve 70 may be viewed.
The main housing 4 is further provided with a helical rib 46, adapted to be seated in the helical groove 74 on the outer surface of the dose dial sleeve 70. In one preferred arrangement, the helical rib 46 extends for a single sweep of the inner surface of the main housing 4. A first stop is provided between the splines 42 and the helical rib. A second stop, disposed at an angle of 180″ to the first stop, is formed by a frame surrounding the window 44 in the main housing 4.
Returning to FIGS. 1-5, a dose dial grip 76 is disposed about an outer surface of the second end of the dose dial sleeve 70. An outer diameter of the dose dial grip 76 preferably corresponds to the outer diameter of the main housing 4. The dose dial grip 76 is secured to the dose dial sleeve 70 to prevent relative movement between these two components. The dose dial grip 76 is provided with a central opening 78. An annular recess 80 located in the second end of the dose dial grip 76 extends around the opening 78. A button 82 of generally ‘T’ section is provided at a second end of the device. A stem 84 of the button may extend through the opening 78 in the dose dial grip 76, through the inner diameter of the extension 38 of the drive sleeve 30 and into the receiving recess 26 at the proximal end of the spindle 20. The stem 84 is retained for limited axial movement in the drive sleeve 30 and against rotation with respect thereto. A head 85 of the button 82 is generally circular. A skirt 86 extends from a periphery of the head 85. The skirt 86 is adapted to be seated in the annular 10 recess 80 of the dose dial grip 76.
Operation of the drug delivery device is described with reference to FIGS. 9, 10 and 11. In FIGS. 9, 10 and 11 arrows, A, B, C, D, E, F and G represent the respective movements of the button 82, the dose dial grip 76, the dose dial sleeve 70, the driver 30, the clutch 60, the clicker 50 and the part nut 40 in one arrangement.
To dial a dose in the arrangement illustrated in FIG. 9, a user rotates the dose dial grip 76 (arrow B). With the clicker 50 and clutch 60 engaged, the driver 30, the clicker 50, the clutch 60 and the dose dial sleeve 70 rotate with the dose dial grip 76. Torque is transmitted through the saw teeth 56, 66 between the clicker 50 and the clutch 60. A flexible arm 52 deforms and drags a toothed member 54 over the splines 42 to produce a click. Preferably, the splines 42 are disposed such that each click corresponds to a conventional unit dose, or the like.
The helical groove 74 on the dose dial sleeve 70 and the helical groove in the driver 30 have the same lead. This allows the dose dial sleeve 70 (arrow C) to extend away from the main housing 4 (See, also FIG. 15). In this manner, the driver 30 (arrow D) climbs the spindle 20 at the same rate. At the limit of travel, a radial stop 104 (See, e.g., FIG. 12) on the dose dial sleeve 70 engages either a first stop or a second stop provided on the main housing 4 to prevent further movement. Rotation of the spindle 20 is prevented due to the opposing directions of the overhauled and driven threads on the spindle 20. The part nut 40, keyed to the main housing 4, is advanced along the intermediate thread 36 by the rotation of the drive sleeve 30 (arrow D).
As mentioned above, a first helical groove form 19 extends from a first or distal end of a spindle 20 towards the proximal end. This first helical groove form 19 extends roughly half the length of the spindle 20. The spindle 20 is of generally circular in cross section however other arrangements may also be used. The distal end of the spindle 20 is threadedly extended through the threaded opening 18 in the insert 16. A pressure foot 22 is located at the first end or distal end of the spindle 20 and disposed to abut a second end of the cartridge piston 10.
A second helical groove form 24 extends from a proximal end of the spindle 20. As illustrated, the second helical groove form 24 comprises a series of part male helical grooves rather than a complete helical groove form. The driver 30 comprises an inner helical groove that extends along an internal surface of the driver 30. As illustrated, this inner helical groove extends along the entire internal surface of the driver from the distal to the proximal end of the driver 30. The second male helical groove form 24 of the spindle 20 is adapted to work within this helical groove.
Although the spindle 20 and the driver 30 arrangement illustrated in FIGS. 1-13 has certain advantages as described and discussed in
WO 2004/078293, this spindle and driver arrangement have certain design limitations. For example, the fabrication of the spindle and driver presents certain manufacturing challenges. As described above, this prior art design comprises a spindle 20 comprising two opposite handed groove forms 19, 24. The first groove form 19 is a female groove form and this female groove form mates with the threaded insert 16 of the main outer diameter of the cylindrical form. The second groove form 24 comprises a plurality of male protrusions that engage with the continuous groove in the driver 30. This continuous groove is molded along the entire length of the internal surface of the driver 30.
In this prior art drug delivery device, when the driver 30 is rotated relative to the spindle 20 during dose setting, because the driver is coupled to the number sleeve which is threaded to the housing, the driver 30 moves axially. The axial distance moved by the driver 30 will be dependent upon the pitch of the number sleeve groove 74 which is generally similar to the pitch of the continuous internal groove on the driver 30. As such, this prior art spindle 20 and driver 30 arrangement requires that the driver 30 be provided with an internal helical groove over roughly the entire inner surface of the driver 30. In this arrangement, the driver 30 does not disengage from the spindle helical groove 24 during either a dose setting step or during a dose administration step.
This arrangement, therefore, presents certain design and manufacturing challenges. For example, during the molding of driver 30 and in particular, during the process of molding the internal helical groove of driver 30, this step requires that a threaded core pin be spun out of the driver during a de-molding step from the injection mold tooling. This processing step has a disadvantages. For example, rotating the threaded core pin requires complex gear mechanisms within the molding tool, with flexible water cooling pipes or sealed rotating joints required to enable this rotating core pin to be cooled. Rotating the core extends the cycle time of the tool and generally adds tool complexity and increased maintenance costs.
There is, therefore, a general need to take these issues into consideration in the design and development of a spindle for certain drug delivery devices, such as reusable (i.e., resettable) or disposable (i.e., non-resettable) drug delivery devices.